Method of producing a transistor

ABSTRACT

THE INVENTION RELATES TO A METHOD OF PRODUCING A TRANSISTOR, SUCH AS A CONTROL TRANSISTOR IN WHICH THE EMITTER REGIONS ARE FORMED BY DIFFUSUION THROUGH STRIP-LIKE APERTURES IN AN INSULATING LAYER ON A SEMICONDUCTOR BODY. THE   STRIPS ARE POSITIONED SIDE BY SIDE AND DECREASE IN WIDTH IN THE DIRECTION OF SUCCESSION OF THE STRIPS.

June 27, 1972 R. KAISER 3,673,012

METHOD OF PRODUCING A TRANSISTOR Filed July 29, 1969 2 Sheets-Sheeb'l Fig. I

In yen/or Ral nhold Kiszr LY 25mm 5' 744,8

fitto'mzys June 27, 1972 R. KAISER 3,673,012

METHOD OF PRODUCING A TRANSISTOR Filed July 29, 1969 ZSheets-Sheet 2 Fig. 3

lnren/ar Reinhold Ka is an United States Patent O 3,673,012 METHOD OF PRODUCING A TRANSISTOR Reinhold Kaiser, Heilbronn, Germany, assignor to Telefunken Patentverwertungsgesellschaft m.b.H., Ulm

(Danube), Germany Filed July 29, 1969, Ser. No. 845,773 Claims priority, application Germany, Aug. 1, 1968, P 17 64 766.4 Int. Cl. H01] 7/44 US. Cl. 148-187 2 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a method of producing a transistor, such as a control transistor in which the emitter regions are formed by diffusion through strip-like apertures in an insulating layer on a semiconductor body. The strips are positioned side by side and decrease in width in the direction of succession of the strips.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION According to the invention, there is provided a method of producing a transistor, in particular a control transistor, in which the emitter diffusion is effected through striplike apertures in an insulating layer present on the semiconductor body, and in which the strip-like apertures are of different widths.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a perspective of a semiconductor body with an insulating layer therein;

FIG. 2 is a view similar to FIG. 1 with an aperture for the diffusion of the base material removed from the insulating layer;

FIG. 3 shows the formation of strip-like apertures for diffusion of the emitter material, and

FIG. 4 shows the finished transistor.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to produce a transistor according to the invention, the starting point is for example a semiconductor body 1 of silicon as shown in FIG. 1, which is of n-type conductivity for example, and has "a specific resistance of about ohm cm. An insulating layer 2, which may consist of silicon dioxide or of silicon nitride for example, is applied to this semiconductor body. The

3,673,012 Patented June 27, 1972 ice thickness of the insulating layer may amount to I for example.

A base window 3, the size of which may be 40 1. by

. 60p. for example, is formed in the insulating layer 2 as shown in FIG. 2. The base region is diffused into the semiconductor body through this base window for example by diffusing in boron at a temperature of 1100 C. The thickness of the base region may amount to 6p for example.

After or during the base diifusion, oxidation is again effected so that the base window 3 is again covered with an oxide layer 4. Emitter diffusion windows 5, 6, 7, which according to the invention have different width, are then formed in this oxide layer 4, as shown in FIG. 3. As a result, the emitter regions diffused into the semiconductor body also have different widths The emitter diffusion windows which are disposed parallel to one another are selected in the example so that their width decreases from left to right. Consequently, the diffusion window 5 has the greatest 'width, the middle diffusion window 6 the second greatest width, while the right-hand diffusion window 7 has the narrowest width. The width of the left-hand emitter difiusion window may be 6,11 for example, that of the middle emitter diffusion window 6 may be 4 for example, and that of the right-hand emitter dilfusion window 7 be 2; for example. A greater or smaller number of emitter diffusion windows may, of course, be disposed side by side. The length of the strip-like emitter difiusion windows 5, 6 and 7 illustrated in FIG. 3 may be 30p. for example.

The production of the emitter regions in the semiconductor body is effected by means of a common diffusion through the individual emitter diffusion windows. That is to say, impurities are diffused into the semiconductor body or into the base region already present in the semiconductor body, through all the emitter diffusion windows in a common diffusion process. A suitable doping material for producing the emitter regions is phosphorus for example, which is diffused into the semiconductor body at a temperature of 1100 C. for example.

It has now been found that a planar transistor, or indeed any transistor, wherein the emitter diifusion is effected through emitter diffusion windows of different widths into an insulating layer present on the semiconductor body and serving as a diffusion mask, surprisingly has particularly satisfactory control characteristics.

Making of contact to the emitter regions difiused into the semiconductor body is effected by vapour deposition of contact-making material on the regions of the semiconductor surface exposed through the emitter diffusion windows 5, 6 and 7. In order to make contact to the base region, apertures must be formed in the oxide layer 4, which is not illustrated in FIG. 3.

FIG. 4 shows the control transistor with contacts fully provided. As this figure shows, contact is made both to the emitter regions and to the base region by means of a comb-like structure. The common emitter electrode is designated by 8 in FIG. 4, while the base electrode has the reference numeral 9.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a method of producing a transistor the improvement comprising forming the emitter of the transistor by the steps of: forming an insulating layer on a surface of a semiconductor body containing a base region which extends to said surface; removing portions of said insulating layer overlying the base region to form a plurality of strip-like apertures of ditferent width in the insulating layer; and difiusing emitter material through said striplike apertures into the base region in said semiconductor body.

2. In a method of producing a transistor the improvement comprising forming the emitter of the transistor by the steps of: forming an isulating layer on a surface of a semiconductor body; removing strip-like portions'of said insulating layer in spaced side by side relationship to form strip-like apertures of diiferent widths in the insulating layer, said strip-like portions haying decreasing widths 15 29- 573; 317 235 R in the direction of the succession of said strip-like portions; and diflusing emitter material through said strip-like apertures into said semiconductor body.

References Cited UNITED STATES PATENTS 3,412,460 11/1968 Lin 148-187 3,418,181 12/1968 Robinson 148187 L. DEWAYNE RUTLEDGE, Primary Examiner J. M. DAVIS, Assistant Examiner US. Cl. X.R. 

